U.S. patent application number 14/646408 was filed with the patent office on 2015-10-29 for assisting apparatus for assisting in performing a brachytherapy.
The applicant listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to Shyam Bharat, Sandeep Dalal, Ehsan Dehghan Marvast, Jochen Kruecker, Cynthia Ming-fu Kung, Amir Mohammad Tahmasebi Maraghoosh.
Application Number | 20150306426 14/646408 |
Document ID | / |
Family ID | 49709786 |
Filed Date | 2015-10-29 |
United States Patent
Application |
20150306426 |
Kind Code |
A1 |
Dehghan Marvast; Ehsan ; et
al. |
October 29, 2015 |
ASSISTING APPARATUS FOR ASSISTING IN PERFORMING A BRACHYTHERAPY
Abstract
The invention relates to an assisting apparatus for assisting in
performing brachytherapy. The position of an introduction element
(17) like a catheter is tracked particularly by using
electromagnetic tracking, while a group of seeds is introduced into
a living object (2). This provides a rough knowledge about the
position of the seeds within the object. An ultrasound image
showing the group is generated depending on the tracked position of
the introduction element and, thus, depending on the rough
knowledge about the position of the seeds, in order to optimize the
ultrasound visualization with respect to showing the introduced
seeds. Based on this optimized ultrasound visualization the
position of a seed of the group is determined, thereby allowing for
an improved determination of seed positions and correspondingly for
an improved brachytherapy performed based on the determined
positions.
Inventors: |
Dehghan Marvast; Ehsan; (New
York, NY) ; Tahmasebi Maraghoosh; Amir Mohammad;
(Ridgefield, CT) ; Bharat; Shyam; (Cortlandt
Manor, NY) ; Dalal; Sandeep; (Cortlandt Manor,
NY) ; Kung; Cynthia Ming-fu; (New York, NY) ;
Kruecker; Jochen; (Washington, DC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
AE Eindhoven |
|
NL |
|
|
Family ID: |
49709786 |
Appl. No.: |
14/646408 |
Filed: |
November 8, 2013 |
PCT Filed: |
November 8, 2013 |
PCT NO: |
PCT/IB2013/059989 |
371 Date: |
May 21, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61735669 |
Dec 11, 2012 |
|
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|
Current U.S.
Class: |
600/424 ;
600/8 |
Current CPC
Class: |
A61N 5/1048 20130101;
A61B 2090/378 20160201; A61B 2034/104 20160201; A61B 2034/2051
20160201; A61B 8/0841 20130101; A61B 8/4245 20130101; A61N 5/1007
20130101; A61N 2005/1074 20130101; A61B 8/0833 20130101; A61B
8/5269 20130101; A61N 2005/1012 20130101; A61N 5/1071 20130101;
A61B 8/483 20130101; A61B 2017/3411 20130101; A61N 5/103 20130101;
A61N 5/1027 20130101; A61N 2005/1024 20130101 |
International
Class: |
A61N 5/10 20060101
A61N005/10; A61B 8/08 20060101 A61B008/08 |
Claims
1. An assisting apparatus for assisting in performing
brachytherapy, during which a brachytherapy seed group including at
least one brachytherapy seed is introduced into a living object by
using an introduction element, the apparatus comprising: a tracking
unit for tracking the position of the introduction element during
the introduction of the group into the living object, an ultrasound
unit for generating an ultrasound image of the living object,
wherein the ultrasound image shows the group within the living
object, wherein the generation of the ultrasound image is
controlled depending on the tracked position of the introduction
element, and a seed position determining unit for determining the
position of a brachytherapy seed of the group depending on the
generated ultrasound image.
2. The assisting apparatus as defined in claim 1, wherein the
ultrasound unit is adapted to generate an ultrasound image, before
the group is introduced into the living object and an actual
ultrasound image, after the group has been introduced into the
living object, wherein the seed position determining unit is
adapted to register the ultrasound images with respect to each
other, to generate a subtraction image by subtracting the
registered ultrasound images from each other and to determine the
position of a brachytherapy seed of the group depending on the
generated subtraction image.
3. The assisting apparatus as defined in claim 1, wherein several
groups of brachytherapy seeds are consecutively introduced into the
living object by using the introduction element, wherein each group
includes at least one brachytherapy seed, the ultrasound unit
adapted to generate an actual ultrasound image, after a group has
been introduced into the living object, wherein the seed position
determining unit is adapted to determine the positions of
brachytherapy seeds of groups already introduced into the living
object depending on the generated actual ultrasound image, in order
to allow for an introduction of further groups depending on the
positions of the brachytherapy seeds of groups already
introduced.
4. The assisting apparatus as defined in claim 3, wherein the seed
position determining unit is adapted to: register the actual
ultrasound image and a previous ultrasound image, which has been
acquired after a previous group and before the actual group has
been introduced, with respect to each other, generate a subtraction
image by subtracting the registered ultrasound images from each
other, determine the positions of the brachytherapy seeds of the
actually introduced group depending on the subtraction image,
provide the positions of the brachytherapy seeds of groups having
been introduced into the living object before the actual group has
been introduced, combine the actually determined positions and the
provided positions for determining the positions of all groups
already introduced into the living object.
5. The assisting apparatus as defined in claim 3, wherein the
apparatus further comprises a region of interest determining unit
for determining a region of interest to be treated within the
living object depending on the generated actual ultrasound image,
in order to allow for an introduction of further groups also
depending on the region of interest determined depending on the
actual ultrasound image.
6. The assisting apparatus as defined in claim 3, wherein the
apparatus further comprises: a treatment plan providing unit for
providing a treatment plan defining a spatial arrangement of
brachytherapy seeds within the living object, wherein the
introduction element is adapted to introduce the groups in
accordance with the treatment plan, a treatment plan updating unit
for updating the treatment plan based on the determined positions
of the brachytherapy seeds of the groups already introduced into
the living object, wherein the introduction element is adapted to
introduce further groups depending on the updated treatment
plan.
7. The assisting apparatus as defined in claim 6, wherein the
apparatus comprises a region of interest determining unit for
determining a region of interest to be treated within the living
object depending on the generated actual ultrasound image, wherein
the treatment plan updating unit adapted to update the treatment
plan also based on the determined region of interest.
8. The assisting apparatus as defined in claim 7, wherein the
provided treatment plan depends on a region of interest, which is
shown in a base ultrasound image and which is to be treated by the
brachytherapy seeds, wherein the base ultrasound image has been
acquired, before any group has been introduced into the living
object, wherein the region of interest determining unit is adapted
to generate a registration transformation registering the base
ultrasound image and the actual ultrasound image with respect to
each other and to update the region of interest shown in the base
ultrasound image by using the registration transformation, wherein
the treatment plan updating unit is adapted to update the treatment
plan based on the determined positions of the brachytherapy seeds
of the groups already introduced into the living object and based
on the updated region of interest.
9. The assisting apparatus as defined in claim 1, wherein the
ultrasound unit is adapted to use a steerable ultrasound beam for
generating the ultrasound image, wherein the ultrasound beam is
controlled depending on the tracked position of the introduction
element.
10. The assisting apparatus as defined in claim 1, wherein the
ultrasound unit is adapted to generate a compound ultrasound image
as the ultrasound image by acquiring several ultrasound images
which correspond to different ultrasound beam directions and by
combining the several ultrasound images.
11. A brachytherapy system for applying brachytherapy to a living
object, the brachytherapy system comprising: an introduction
element for introducing several groups of brachytherapy seeds
consecutively into the living object in accordance with the
treatment plan, and an assisting apparatus for assisting in
performing the brachytherapy as defined in claim 1.
12. An assisting method for assisting in performing brachytherapy,
during which a brachytherapy seed group including at least one
brachytherapy seed is introduced into a living object by using an
introduction element, the assisting method comprising: tracking the
position of the introduction element during the introduction of the
group into the living object by a tracking unit, generating an
ultrasound image of the living object by an ultrasound unit,
wherein the ultrasound image shows the group within the living
object, wherein the generation of the ultrasound image is
controlled depending on the tracked position of the introduction
element, and determining the position of a brachytherapy seed of
the group depending on the generated ultrasound image by a seed
position determining unit.
13. An assisting computer program for assisting in performing
brachytherapy, during which a brachytherapy seed group including at
least one brachytherapy seed is introduced into a living object by
using an introduction element, the assisting computer program
comprising program code means for causing an assisting apparatus as
defined in claim 1 to carry out the assisting method, when the
computer program is run on a computer controlling the assisting
apparatus.
Description
FIELD OF THE INVENTION
[0001] The invention relates to an assisting apparatus, an
assisting method and an assisting computer program for assisting in
performing a brachytherapy. The invention relates further to a
brachytherapy system comprising the assisting apparatus.
BACKGROUND OF THE INVENTION
[0002] US 2009/0198094 A1 discloses an apparatus for determining a
distribution of a selected therapy in a target volume. The
apparatus comprises a three-dimensional ultrasound transducer for
capturing volume data from the target volume and a computing device
in communication with the three-dimensional ultrasound transducer
for receiving the volume data. The computing device is further
adapted to determine the distribution of the selected therapy in
the target volume along a set of planned needle trajectories using
the volume data, wherein at least one of the needle trajectories is
oblique to at least one other of the planned needle trajectories.
The quality of the ultrasound imaging may be reduced, which in turn
may lead to a reduced accuracy of the determination of the
distribution of the selected therapy in the target volume. If a
brachytherapy is based on this determined distribution having a
reduced accuracy, also the quality of the brachytherapy is
reduced.
SUMMARY OF THE INVENTION
[0003] It is an object of the present invention to provide an
assisting apparatus, an assisting method and an assisting computer
program for assisting in performing brachytherapy, which allow for
an improved quality of the brachytherapy. It is a further object of
the present invention to provide a brachytherapy system for
applying a brachytherapy to a living object, wherein the
brachytherapy system comprises the assisting apparatus.
[0004] In a first aspect of the present invention an assisting
apparatus for assisting in performing brachytherapy is presented,
during which a brachytherapy seed group including at least one
brachytherapy seed is introduced into a living object by using an
introduction element, the apparatus comprising: [0005] a tracking
unit for tracking the position of the introduction element during
the introduction of the group into the living object, [0006] an
ultrasound unit for generating an ultrasound image of the living
object, wherein the ultrasound image shows the group within the
living object, wherein the generation of the ultrasound image is
controlled depending on the tracked position of the introduction
element, and [0007] a seed position determining unit for
determining the position of a brachytherapy seed of the group
depending on the generated ultrasound image.
[0008] Since the tracking unit tracks the position of the
introduction element during the introduction of the group into the
living object, it is already roughly known where the respective
group of brachytherapy seeds has been placed within the living
object. This rough knowledge about the position of the seeds within
the living object can be used by the ultrasound unit for optimizing
the ultrasound imaging for imaging in this roughly known region of
the living object, thereby allowing for an improvement of the
ultrasound visualization. Since the position of the brachytherapy
seed of the group is determined based on the ultrasound image
obtained by the improved ultrasound visualization, also the
determination of the position of the brachytherapy seed can be
performed with improved accuracy. This in turn allows for an
improved quality of a brachytherapy, which is based on the
determined position of the brachytherapy seed.
[0009] The group of at least one brachytherapy seed can comprise
one or several brachytherapy seeds. The living object is
preferentially a human being or an animal. The brachytherapy is
preferentially a low dose rate (LDR) brachytherapy, which is
especially adapted for treating a prostate.
[0010] The tracking unit is preferentially adapted to
electromagnetically track the position of the introduction element
during the introduction of the group into the living object.
Moreover, the tracking unit can be used to globally or roughly find
a target region with introduced seeds, wherein then an ultrasound
beam can be directed to this globally or roughly found target
region.
[0011] It is preferred that the ultrasound unit is adapted to
generate an ultrasound image, before the group is introduced into
the living object, and an actual ultrasound image, after the group
has been introduced into the living object, wherein the seed
position determining unit is adapted to register the ultrasound
images with respect to each other, to generate a subtraction image
by subtracting the registered ultrasound images from each other and
to determine the position of a brachytherapy seed of the group
depending on the generated subtraction image. The registration is
preferentially a deformable registration.
[0012] The ultrasound image, which has been generated before the
group is introduced into the living object, can be a base
ultrasound image, which has been generated, before any
brachytherapy seed has been introduced into the living object. In
this case the positions of all brachytherapy seeds, which have
already been introduced into the living object, can be determined
directly from the subtraction image. However, if several groups of
brachytherapy seeds are consecutively introduced into the living
object by using the introduction element, wherein each group
includes at least one brachytherapy seed, for each group of
brachytherapy seeds an actual ultrasound image can be generated,
after the respective group has been introduced into the living
object, and a previous ultrasound image can be generated, before
the respective group has been introduced into the living object and
after the previous group of brachytherapy seeds has been introduced
into the living object. The kind of imaging may be called
"incremental imaging". For each group of brachytherapy seeds a
subtraction image can be generated by subtracting the respective
actual and previous ultrasound images from each other, wherein the
respective subtraction image can be used for determining the
positions of the one or several brachytherapy seeds of the
respective group. Since this determination of the positions of the
brachytherapy seed is performed for each group that have already
been introduced into the living object, the positions of all
brachytherapy seeds introduced into the living object can be
determined by incremental imaging.
[0013] Generally, an ultrasound image may comprise bright image
artifacts, which can be caused by microcalcifications in the living
object and which may be misclassified as being brachytherapy seeds.
These bright image artifacts are supposed to be present in
subsequent images such that, if these images are subtracted from
each other, the resulting subtraction image should not comprise
these bright image artifacts. By determining the positions of the
brachytherapy seeds based on the subtraction images the likelihood
of a misclassification, i.e. the determination of a supposed seed
position which in fact is, for instance, a microcalcification
position, can therefore be reduced, thereby further improving the
quality of determining the positions of the brachytherapy seeds
and, thus, the quality of the brachytherapy, which is based on
these determined positions.
[0014] It is further preferred that several groups of brachytherapy
seeds are consecutively introduced into the living object by using
the introduction element, wherein each group includes at least one
brachytherapy seed, wherein the ultrasound unit is adapted to
generate an actual ultrasound image, after a group has been
introduced into the living object, wherein the seed position
determining unit is adapted to determine the positions of
brachytherapy seeds of groups already introduced into the living
object depending on the generated actual ultrasound image, in order
to allow for an introduction of further groups depending on the
positions of the brachytherapy seeds of groups already introduced.
In particular, the seed position determining unit can be adapted to
a) register the actual ultrasound image and a previous ultrasound
image, which has been acquired after a previous group and before
the actual group has been introduced, with respect to each other,
b) generate a subtraction image by subtracting the registered
ultrasound images from each other, c) determine the positions of
the brachytherapy seeds of the actually introduced group depending
on the subtraction image, d) provide the positions of the
brachytherapy seeds of groups having been introduced into the
living object before the actual group has been introduced, and e)
combine the actually determined positions and the provided
positions for determining the positions of all groups already
introduced into the living object. This allows considering
modifications in the positions of the already introduced
brachytherapy seeds, which may be caused by a swelling of the
living object, for instance, of the prostate, while introducing the
further brachytherapy seeds, thereby allowing for a further
improved quality of the brachytherapy.
[0015] In a preferred embodiment the apparatus further comprises a
region of interest determining unit for determining a region of
interest to be treated within the living object depending on the
generated actual ultrasound image, in order to allow for an
introduction of further groups also depending on the region of
interest determined depending on the actual ultrasound image. The
region of interest to be treated within the living object is, for
instance, the prostate or a certain region within the prostate like
a tumor region within the prostate. The region of interest
determining unit can also be adapted to determine, i.e. segment,
further elements of the living object, like vessels, organs, et
cetera, based on the actual ultrasound image. The region of
interest, i.e. the location and/or shape of the region of interest,
and optionally further determined elements may change during the
introduction of the several groups of brachytherapy seeds.
Considering this possible change while introducing the several
groups of brachytherapy seeds can further improve the accuracy of
determining the positions of the brachytherapy seeds and, thus, the
quality of the brachytherapy applied depending on the determined
positions.
[0016] The apparatus preferentially further comprises a) a
treatment plan providing unit for providing a treatment plan
defining a spatial arrangement of brachytherapy seeds within the
living object, wherein the introduction element is adapted to
introduce the groups in accordance with the treatment plan, and b)
a treatment plan updating unit for updating the treatment plan
based on the determined positions of the brachytherapy seeds of the
groups already introduced into the living object, wherein the
introduction element is adapted to introduce further groups
depending on the updated treatment plan. The treatment plan
updating unit may be further adapted to update the treatment plan
also based on the determined region of interest and optionally
further elements of the living object, which may have been
determined based on the actual ultrasound image.
[0017] The provided treatment plan depends preferentially on a
region of interest and optionally on further elements of the living
object like vessels, organs et cetera, which are shown in a base
ultrasound image, wherein the region of interest should be treated
by the brachytherapy seeds, wherein the base ultrasound image has
been acquired, before any group of brachytherapy seeds has been
introduced into the living object, wherein the region of interest
determining unit is adapted to generate a registration
transformation registering the base ultrasound image and the actual
ultrasound image with respect to each other and to update the
region of interest and the optional further elements shown in the
base ultrasound image by using the registration transformation, and
wherein the treatment plan updating unit is adapted to update the
treatment plan based on the determined positions of the
brachytherapy seeds of the groups already introduced into the
living object, based on the updated region of interest and
optionally also based on the updated further elements. It is
therefore not necessarily required to segment the region of
interest and the optional further elements in each actual
ultrasound image, which may be acquired during incremental imaging,
because the actual region of interest, i.e. the actual location
and/or shape of the region of interest, and also the optional
actual further elements can readily be determined by applying the
registration transformation to the region of interest and the
optional further elements initially determined in the base
ultrasound image. For instance, in the base ultrasound image the
region of interest and also further parts of the living object may
be segmented for determining their locations and/or shapes within
the living object, wherein to these segmentations the registration
transformation can be applied, in order to provide updated
segmentations, which can be used for updating the treatment
plan.
[0018] The registration between the actual ultrasound image and the
base ultrasound image can be a direct registration, i.e. each
actual ultrasound image, which has been generated for the
respective group, can be registered with the base ultrasound image,
for generating for the respective group the registration
transformation. However, also incremental registration can be used
for finally obtaining a registration between the base ultrasound
image and the actual ultrasound image of the respective group. That
means the base ultrasound image can be registered with the actual
ultrasound image of the first group, the actual ultrasound image of
the first group can be registered with the actual ultrasound image
of the second group, the actual ultrasound image of the second
group can be registered with the actual ultrasound image of the
third group, et cetera, in order to have the actual ultrasound
images of each group registered with the base ultrasound image.
[0019] It is further preferred that the ultrasound unit is adapted
to use a steerable ultrasound beam for generating the ultrasound
image, wherein the ultrasound beam is controlled depending on the
tracked position of the introduction element. Moreover, it is
preferred that the ultrasound unit is adapted to generate a
compound ultrasound image as the ultrasound image by acquiring
several ultrasound images which correspond to different ultrasound
beam directions and by combining the several ultrasound images.
This allows providing an ultrasound image showing all brachytherapy
seeds, which have already been introduced into the living object,
even if in a certain ultrasound beam direction one or several
brachytherapy seeds are not visible because of, for example,
shading effects. This allows for a further improved accuracy of
determining the positions of the brachytherapy seeds within the
living object, which in turn leads to a further improved quality of
the brachytherapy performed based on the determined positions.
[0020] In a further aspect of the present invention a brachytherapy
system for applying brachytherapy to a living object is presented,
wherein the brachytherapy system comprises: [0021] an introduction
element for introducing several groups of brachytherapy seeds
consecutively into the living object in accordance with the
treatment plan, and [0022] an assisting apparatus for assisting in
performing the brachytherapy as defined in claim 1.
[0023] In a further aspect of the present invention an assisting
method for assisting in performing brachytherapy is presented,
during which a brachytherapy seed group including at least one
brachytherapy seed is introduced into a living object by using an
introduction element, wherein the assisting method comprises:
[0024] tracking the position of the introduction element during the
introduction of the group into the living object by a tracking
unit, [0025] generating an ultrasound image of the living object by
an ultrasound unit, wherein the ultrasound image shows the group
within the living object, wherein the generation of the ultrasound
image is controlled depending on the tracked position of the
introduction element, and [0026] determining the position of a
brachytherapy seed of the group depending on the generated
ultrasound image by a seed position determining unit.
[0027] In a further aspect of the present invention an assisting
computer program for assisting in performing brachytherapy is
presented, during which a brachytherapy seed group including at
least one brachytherapy seed is introduced into a living object by
using an introduction element, the assisting computer program
comprising program code means for causing an assisting apparatus as
defined in claim 1 to carry out the assisting method as defined in
claim 12, when the computer program is run on a computer
controlling the assisting apparatus.
[0028] It shall be understood that the assisting apparatus of claim
1, the brachytherapy system of claim 11, the assisting method of
claim 12, and the assisting computer of claim 13 have similar
and/or identical preferred embodiments, in particular, as defined
in the dependent claims.
[0029] It shall be understood that a preferred embodiment of the
invention can also be any combination of the dependent claims or
above embodiments with the respective independent claim.
[0030] These and other aspects of the invention will be apparent
from and elucidated with reference to the embodiments described
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] In the following drawings:
[0032] FIG. 1 shows schematically and exemplarily an embodiment of
a brachytherapy system for applying brachytherapy to a person,
[0033] FIG. 2 shows schematically and exemplarily elements of the
brachytherapy system shown in FIG. 1 in more detail,
[0034] FIGS. 3 to 6 illustrate different ultrasound beam
configurations that may be used for ultrasonically imaging
brachytherapy seeds within the living being,
[0035] FIG. 7 illustrates generation of a subtraction image,
and
[0036] FIGS. 8 and 9 show flowcharts exemplarily illustrating
embodiments of a brachytherapy method for applying brachytherapy to
a living object.
DETAILED DESCRIPTION OF EMBODIMENTS
[0037] FIG. 1 shows schematically and exemplarily an embodiment of
a brachytherapy system 14 for applying brachytherapy to a person 2
lying on a support means 3 like a table. The brachytherapy system
14 is adapted to perform a LDR brachytherapy, wherein several
groups of brachytherapy seeds are consecutively introduced into the
person 2 by using a placing unit 5. The placing unit 5 is
schematically and exemplarily shown in more detail in FIG. 2.
[0038] The placing unit 5 comprises an introduction element 17 for
introducing the several groups of brachytherapy seeds consecutively
into the person 2 in accordance with a treatment plan. In this
embodiment the introduction element 17 is a catheter. The several
groups of brachytherapy seeds can be manually introduced into the
person 2 by using a grid template 13. In FIG. 2 reference number 18
indicates a hand of an operator like a physician introducing
brachytherapy seeds into the person 2 by using the catheter 17. The
placing unit 5 further comprises an ultrasound probe 15, which is
connected to an ultrasound control unit 7, for generating an
ultrasound image of the person 2. The ultrasound probe 15 and the
grid template 13 are both attached to a holding element 16. The
ultrasound probe 15 is preferentially a transrectal ultrasound
(TRUS) probe. The TRUS probe 15 can be adapted to acquire
three-dimensional life images. It can allow for an automatic
acquisition of an entire volume without having to mechanically move
the TRUS probe 15. However, the ultrasound probe can also be a
two-dimensional ultrasound probe, in particular, a biplane
two-dimensional TRUS probe, wherein in this case preferentially the
ultrasound probe is translated and/or rotated to reconstruct a
three-dimensional image. In particular, the ultrasound probe and
the ultrasound control unit can be adapted to use beam steering and
spatial compounding for forming the three-dimensional image. In the
following different techniques for constructing the
three-dimensional image will be exemplarily described in more
detail.
[0039] FIG. 3 shows schematically and exemplarily two brachytherapy
seeds 20, 21, which have been introduced into the prostate 19 of
the person 2. The ultrasound probe 115 shown in FIG. 3 has a
relatively large size transducer resulting in a field of view 24,
26, which completely covers the prostate 19. FIG. 3 illustrates two
acquisition directions, i.e. two directions of the ultrasound beam,
a first direction 23 with the corresponding field of view 24 and a
second direction 25 with a corresponding field of view 26. In this
example the three-dimensional image is generated by compounding
images acquired with different beam angles, i.e. acquired in
different acquisition directions, without changing the position of
the ultrasound probe 115. Each brachytherapy seed 20, 21 within the
tissue of the prostate 19 is interrogated by different beam
angles.
[0040] FIGS. 4a and 4b show another embodiment of an ultrasound
probe 215, which has a smaller field of view 28, 30. The transducer
size and, thus, the field of views 28, 30 are not sufficiently
large to cover the whole region of interest, i.e. in this
embodiment the complete prostate 19. However, also the ultrasound
probe 215 has beam steering capabilities, and the ultrasound probe
215 can be moved relative to the prostate 19 such that a
three-dimensional image can be constructed via spatial compounding
of different images acquired from different probe positions. In
particular, FIG. 4a illustrates the acquisition of a first image by
using a first acquisition direction 27 and a corresponding field of
view 28 at a first position of the ultrasound probe 215 relative to
the prostate 19 and FIG. 4b illustrates the acquisition of a second
image in a second acquisition direction 29 by using a corresponding
field of view 30 at a second position of the ultrasound probe 215
relative to the prostate 19. The difference with respect to the
positions of the ultrasound probe 215 relative to the prostate 19
is indicated in FIG. 4a by the double arrow 31.
[0041] In a further example during acquiring the ultrasound images
the beam angle may be fixed such that each brachytherapy seed is
interrogated by one beam angle only, wherein the probe position may
be changed, in order to simulate the effects of beam steering.
Desired effects of beam steering, which can be obtained by steering
the beam used for generating the ultrasound image or by simulating
such a beam steering, will in the following be described with
reference to FIGS. 5 and 6.
[0042] FIG. 5 illustrates the acquisition of an ultrasound image by
using the ultrasound probe 215 in a first direction 33 and in a
second direction 36. The corresponding fields of view are indicated
in FIG. 5 by reference numbers 38 and 37, respectively. The
brachytherapy seed 32 primarily reflects the ultrasound wave away
from the ultrasound probe 215 in the direction indicated by the
arrow 34. The remaining low-intensity echo will generally be
obscured by background speckle noise in the acquired image and
cannot be seen well in the image. However, by using beam steering
the acquisition direction can be changed to the second acquisition
direction 35 being substantially perpendicular to the brachytherapy
seed 32 such that the ultrasound beam is substantially reflected
back towards the ultrasound probe 215 in the direction indicated in
FIG. 5 by reference number 35. Thus, by using beam steering the
visibility of a brachytherapy seed in an ultrasound image can be
increased.
[0043] The beam steering technique can also be used to solve a
possibly present obstruction problem caused by a brachytherapy seed
40 located in a shadow of another brachytherapy seed 39 as
exemplarily shown in FIG. 6. The ultrasound image acquired in a
first direction with a corresponding field of view 38 does not
clearly show the brachytherapy seed 40, because it is in the shadow
of the other brachytherapy seed 39. However, an ultrasound image
acquired in a second direction with a corresponding field of view
37 also shows the brachytherapy seed 40 behind the other
brachytherapy seed 39. Thus, the brachytherapy seed 40 in the
shadow of the other brachytherapy seed 39 is clearly visible in the
ultrasound image obtained with a beam angle, which corresponds to
the acquisition direction with the field of view 37 in FIG. 6.
[0044] The ultrasound probe can be adapted to acquire
two-dimensional or three-dimensional ultrasound images, which have
been acquired with different beam angles, wherein these
two-dimensional or three-dimensional ultrasound images can be
compounded to construct a three-dimensional ultrasound image.
However, the ultrasound probe and the ultrasound control unit can
also be adapted to reconstruct a three-dimensional ultrasound image
from several two-dimensional ultrasound images. In particular, the
ultrasound probe and the ultrasound control unit can be adapted to
construct a three-dimensional image by reconstruction of
two-dimensional slices without beam steering.
[0045] For instance, the ultrasound probe and the ultrasound
control unit can be adapted to generate two-dimensional ultrasound
images, which are not compounded, but used to reconstruct a
three-dimensional ultrasound image. Moreover, different
two-dimensional ultrasound images, which represent different planes
within the person 2, which are positioned and/or oriented
differently, can be generated and reconstructed to a
three-dimensional ultrasound image. Furthermore, the ultrasound
probe and the ultrasound control unit can be adapted to generate
different compounded two-dimensional ultrasound images, which are
reconstructed to a three-dimensional ultrasound image, wherein a
two-dimensional compounded ultrasound image can be compounded from
several two-dimensional ultrasound images generated with different
beam angles. The different two-dimensional compounded ultrasound
images can represent different planes within the person 2, which
are positioned and/or oriented differently, wherein these
two-dimensional compounded ultrasound images can be used for
reconstructing the three-dimensional ultrasound image. The
ultrasound probe can also be a three-dimensional ultrasound probe
directly generating a three-dimensional ultrasound image with or
without compounding several three-dimensional ultrasound images. If
several three-dimensional ultrasound images are compounded, the
several three-dimensional ultrasound images can correspond to
different sub-apertures and/or can be associated to different
steering angles and/or can be associated to different spatial
positions of the three-dimensional ultrasound probe. In the latter
case the three-dimensional ultrasound probe may be moved in-between
individual volume acquisitions.
[0046] Referring again to FIG. 1, the brachytherapy system 14
comprises a display 12 for displaying, for instance, the ultrasound
images, determined positions of brachytherapy seeds or of other
elements within the person 2. Moreover, the brachytherapy system 14
comprises an electromagnetic tracking unit 6 for
electromagnetically tracking the position of the introduction
element 17 during the introduction of the groups of brachytherapy
seeds into the person 2. The catheter 17, in particular, the tip of
the catheter 17, comprises a corresponding electromagnetic element,
which can be tracked by the electromagnetic tracking unit 6.
[0047] The ultrasound control unit 7 is preferentially adapted to
control the generation of the ultrasound image depending on the
tracked position of the catheter 17. In particular, if the
ultrasound probe comprises a steerable ultrasound beam for
generating the ultrasound image, the ultrasound beam is
preferentially controlled depending on the tracked position of the
catheter 17, in particular, of the tip of the catheter 17.
Preferentially, the positions of the brachytherapy seeds, which
have actually been introduced into the person 2 by using the
catheter 17, are estimated from the tracked positions of the
catheter 17 at the respective times of deposition. For instance,
the position of a brachytherapy seed relative to the position of
the electromagnetic element at the tip of the catheter can be known
at the time of deposition and used together with the tracked
position of the electromagnetic element for estimating the position
of the actually deposited brachytherapy seed. This information,
i.e. the approximate position of the actually deposited
brachytherapy seed, can be used to control the beam steering of the
ultrasound imaging process to exactly locate the seed. Areas far
away from the approximate position are preferentially excluded from
consideration during the seed detection process. In particular,
based on the approximate positions of the brachytherapy seeds,
which have already been introduced into the person 2, the
ultrasound beam can be steered such that the above described
problems of reflections away from the ultrasound probe and of
brachytherapy seeds in the shadow of other brachytherapy seeds are
reduced, in particular, eliminated. For instance, if the
approximate positions of the brachytherapy seeds indicate a
situation as schematically and exemplarily shown in FIG. 6, the
ultrasound beam of the ultrasound probe can be steered such that at
least one of the images, which are compounded for forming the
three-dimensional image, corresponds to the acquisition direction
with the field of view indicated in FIG. 6 by reference number
37.
[0048] The brachytherapy seeds are deposited by inserting the
catheter 17 filled with one or several brachytherapy seeds and
optionally spacers between several brachytherapy seeds into the
person. The one or several brachytherapy seeds should be arranged
at locations within the person 2, which are defined in the
treatment plan, which may also be regarded as being a dose plan.
The electromagnetic tracking unit 6 together with the
electromagnetic element at the tip of the catheter 17 can assist in
this introduction step by directing the user to the correct
locations, wherein the actual location of the catheter 17 at the
time of seed deposition can be recorded and provided as an
estimation of the seed position to the ultrasound control unit 7
for allowing the ultrasound control unit 7 to perform the
ultrasound imaging under consideration of this estimated seed
position.
[0049] The brachytherapy system 14 further comprises a seed
position determining unit 8 for determining the position of a
brachytherapy seed depending on the generated three-dimensional
ultrasound image. Preferentially, the ultrasound unit formed by one
of the above mentioned ultrasound probes and the ultrasound control
unit 7 is adapted to generate an ultrasound image, before a group
of brachytherapy seeds is introduced into the person 2, and to
generate an actual ultrasound image, after the group has been
introduced into the person 2, wherein the seed position determining
unit 8 is adapted to register the ultrasound images with respect to
each other, to generate a subtraction image by subtracting the
registered ultrasound images from each other and to determine the
position of a brachytherapy seed of the group depending on the
generated subtraction image. The registration is preferentially a
deformable registration. The determined positions of the one or
several brachytherapy seeds of the group are preferentially used
for determining desired positions of brachytherapy seeds of further
groups, which may be introduced to the person 2.
[0050] In particular, for determining the positions of all
brachytherapy seeds, which have already been introduced into the
person 2, the actual ultrasound image and a previous ultrasound
image, which has been acquired after a previous group and before
the actual group has been introduced into the person 2, are
registered with respect to each other. Thus, the last volume image
I.sub.n-1, which has been acquired before the actual seed
deposition, is registered, in particular, elastically and/or
deformably registered, with the actual volume image I.sub.n, which
has been acquired after the actual seed deposition, i.e. a
registration transformation T.sub.n-1.fwdarw.n is calculated. For
performing this registration procedure known registration
algorithms can be used like the "Demons" algorithm or a variant of
this algorithm, which is disclosed, for instance, in the article
"Understanding the "Demon's Algorithm": 3D Non-rigid Registration
by Gradient Descent" by X. Pennec et al., Medical Image Computing
and Computer-Assisted Intervention--MICCAI'99, pages 597 to 606
(1999), which is herewith incorporated by reference. The registered
images may then be subtracted from each other for generating a
subtraction image. A difference image is therefore created, in
which all features present in both images are eliminated, thereby
enhancing those features introduced between the two image
acquisitions, i.e. thereby enhancing the brachytherapy seeds, which
have been introduced into the person 2 during the actual seed
deposition. The positions of the brachytherapy seeds of the
actually introduced group can then be determined in the subtraction
image by using, for instance, known segmentation techniques. This
concept of incremental imaging for detecting the position of a most
recently implanted brachytherapy seed is illustrated in FIG. 7.
[0051] In FIG. 7 a previous image I.sub.n-1 shows the brachytherapy
seeds 52, which have already been implanted, and
microcalcifications 51 within the prostate 19. An actual image
I.sub.n also shows the brachytherapy seeds 52 and the
microcalcifications 51 visible in the previous image I.sub.n-1.
However, in addition the actual image I.sub.n also shows an
actually implanted brachytherapy seed 53. Moreover, the actual
image I.sub.n shows an edema of the prostate, which has grown from
a previous size indicated by the broken line 50 to an actual size
indicated by the solid line 19. In this example the previous image
I.sub.n-1 is deformed to the deformed previous image I'.sub.n-1 by
registering the previous image I.sub.n-1 with the actual image
I.sub.n. The deformed previous image I'.sub.n-1 is then subtracted
from the actual image I.sub.n to generate a subtraction image
I.sub.n,s, in which the newly introduced brachytherapy seed 53 is
visible in an enhanced way. In another example alternatively or in
addition also the previous image I.sub.n-1 may be deformed during
the registration process.
[0052] This technique of incremental imaging can prevent erroneous
classifications of microcalcifications and other bright image
artifacts as brachytherapy seeds. Any seed-like artifact in a base
ultrasound image, which has been acquired before the catheter 17 is
inserted into the person 2 for the first time and which may also be
regarded as being an initial ultrasound image, is generally also
visible in subsequent ultrasound images acquired after each
insertion of the catheter 17 for introducing a group formed of one
or more brachytherapy seeds into the person 2. Since each
subsequent ultrasound image is deformably registered to the
previous ultrasound image and since subtraction images between
successive images are obtained, the seed-like artifacts caused by,
for instance, microcalcifications can be cancelled out and not
erroneously identified as inserted brachytherapy seeds. Moreover,
this incremental technique can at least partly suppress background
speckle noise, which will further enhance the visibility of the
currently implanted one or several brachytherapy seeds. In
addition, by deformably registering images acquired before and
after the last insertion of the catheter for introducing the actual
group of one or several brachytherapy seeds, the positions of the
brachytherapy seeds that were previously implanted at a larger
distance from the ultrasound probe can be preserved, even if these
previous seeds are located in the shadow of the actually newly
implanted brachytherapy seeds, which may be more proximal. Thus,
the incremental technique involving incremental imaging and
incremental determining of the positions of the brachytherapy seeds
can also be used to solve the obstruction problem described above
with reference to FIG. 6.
[0053] For determining the positions of all brachytherapy seeds
introduced into the person 2 the seed position determining unit 8
is further adapted to provide the positions of the brachytherapy
seeds of groups, which have already been introduced into the person
2, before the actual group has been introduced, and to combine the
actually determined positions and the provided positions for
determining the positions of all groups, i.e. of all brachytherapy
seeds of all groups, already introduced into the person 2. For
instance, newly identified seeds S.sub.n,n, i.e. the n-th group of
new seeds in the coordinate system of the actual image I.sub.n ,
can be stored, wherein these new seeds S.sub.n,n can be combined
with all prior seeds S.sub.total,n-1 present in the previous image
I.sub.n-1, wherein the registration transform T.sub.n-1.fwdarw.n
can be applied to the coordinates of the positions of the prior
seeds S.sub.total,n-1, in accordance with following equations:
S.sub.prior,n=T.sub.n-1.fwdarw.n.times.S.sub.total,n-1 (1)
and
S.sub.total,n=S.sub.prior,n.orgate.S.sub.n,n (2)
[0054] The brachytherapy system 14 further comprises a region of
interest determining unit 9 for determining a region of interest to
be treated within the person 2 depending on the generated actual
ultrasound image, in order to allow for an introduction of further
groups also depending on the region of interest, which has been
determined based on the actual ultrasound image. The region of
interest is, for instance, the prostate or a part of the prostate.
In particular, the region of interest may be a tumor region within
the prostate. It can be determined by known segmentation techniques
based on the actual ultrasound image.
[0055] The brachytherapy system 14 further comprises a treatment
plan providing unit 10 for providing a treatment plan defining a
spatial arrangement of brachytherapy seeds within the person 2,
wherein the groups of brachytherapy seeds are introduced into the
person 2 by using the catheter 17 in accordance with the treatment
plan. A treatment plan updating unit 11 updates the treatment plan
based on the determined positions of the brachytherapy seeds of the
groups already introduced into the person 2, based on the region of
interest, i.e. location and/or shape of the region of interest,
determined by using the actual ultrasound image and optionally also
based on the location and/or shape of further elements of the
person 2 like vessels, organs et cetera, which may also be
determined based on the actual ultrasound image.
[0056] The provided treatment plan, i.e. the initial treatment
plan, depends--inter alia--on the region of interest as shown in
the base ultrasound image, which has been acquired, before any
group has been introduced into the person 2. The region of interest
determining unit 9 can be adapted to generate a registration
transformation registering the base ultrasound image and the actual
ultrasound image with respect to each other and to update the
region of interest shown in the base ultrasound image by using the
registration transformation, wherein the treatment plan updating
unit 11 can be adapted to update the treatment plan based on the
determined positions of the brachytherapy seeds of the groups
already introduced into the person 2 and based on this updated
region of interest. The registration can also be used to update the
location and shape of further elements, which are shown in the base
ultrasound image and which may have been used for determining the
initial treatment plan, wherein the treatment plan can be updated
also based on this updated information. The registration of the
actual ultrasound image with the base ultrasound image can be a
direct registration, wherein the actual ultrasound image is
directly registered with the base ultrasound image or an indirect
or incremental registration, wherein the base ultrasound image and
the subsequently consecutively acquired ultrasound images are pair
wise registered with respect to each other, thereby forming a
sequence of incremental registrations defining a registration
transformation between the base ultrasound image and the actual
ultrasound image. The treatment plan, which may also be regarded as
being a dose plan, defines at which positions the brachytherapy
seeds should be placed. The treatment plan preferentially further
defines the radiation dose that the respective brachytherapy seed
should apply to the person.
[0057] For determining the initial treatment plan different
elements shown in the base ultrasound image are preferentially
segmented. For instance, the prostate or a part of the prostate
forming the region of interest, the rectum, the urethra, the
bladder, et cetera are segmented, wherein the initial treatment
plan is preferentially determined such that a prescribed target
dose is applied to the region of interest, while keeping the
radiation dose applied to the other structures minimal. The
segmentation procedure and/or the determination of the treatment
plan based on the resulting segmentations can be performed
manually, semi-automatically or completely automatically.
[0058] The registration transformation T.sub.n-1.fwdarw.n can also
be used to update the segmentations, in particular, the shapes and
locations of all segmentations from the previous ultrasound image
to the actual ultrasound image, wherein based on these updated
segmentations and all locations of already placed brachytherapy
seeds S.sub.total,n the treatment plan updating unit 11 can update
the treatment plan. Preferentially, the treatment plan updating
unit 11 takes into account the already delivered radiation dose,
which is defined by the positions of the already placed
brachytherapy seeds and there dwell times, and the prescribed
radiation dose targets. The positions of the brachytherapy seeds
that still need to be delivered to achieve the prescribed radiation
dose targets are determined based on the already delivered
radiation dose. This updating of the treatment plan is
preferentially performed each time when an incremental ultrasound
image I.sub.n has been acquired. The actual adaptively updated
treatment plan may or may not differ from the previously adaptively
updated treatment plan. If more brachytherapy seeds are needed
according to the latest treatment plan, the brachytherapy seed
insertion continues with the (n+1)-th iteration of catheter
insertion and imaging. Otherwise the procedure is completed.
[0059] Instead of performing incremental registrations
I.sub.n-1.fwdarw.I.sub.n all ultrasound images can be registered
back to the base line ultrasound image I.sub.0. Or, for enhanced
consistency between all registration transformations, the
registrations can be carried out jointly and simultaneously between
I.sub.n-1 and I.sub.n as well as between I.sub.n and I.sub.0.
Considering the base ultrasound image I.sub.0 during the
registration procedure can avoid errors, which may accumulate in
successive incremental image registrations.
[0060] In the following two embodiments of brachytherapy methods
will exemplarily be described with reference to flowcharts shown in
FIGS. 8 and 9. A first embodiment illustrated in FIG. 8 uses
incremental image registration and a second embodiment illustrated
in FIG. 9 uses a registration with the base ultrasound image,
wherein the registrations are used to keep track of segmentations,
in particular, of organ segmentations, and all seed locations, i.e.
all seed positions, throughout the insertion procedure.
[0061] After the brachytherapy method has started in step 301, in
step 302 an initial three-dimensional TRUS volume, i.e. the base
ultrasound image I.sub.0, is acquired. In step 303 segmentations
are created in the base ultrasound image I.sub.0 and an initial
treatment plan is determined based on the created segmentations and
prescribed radiation dose targets. In step 304 a first group
comprising one or several brachytherapy seeds is introduced into
the person 2 by using an introduction element like a catheter or a
needle in accordance with the treatment plan, wherein the position
of the introduction element is electromagnetically tracked during
the introduction of the actual group into the person, especially at
the time of depositing the one or several brachytherapy seeds of
the actual group. After the group has been deposited, the
introduction element is retracted from the person. Then, in step
305 the n-th intra-procedure three-dimensional TRUS volume I.sub.n
is acquired, wherein during the first iteration n is 1. During the
acquisition of the intra-procedure three-dimensional TRUS volume
I.sub.n the ultrasound image generation is controlled depending on
the position of the introduction element during the introduction
procedure tracked in step 304. In step 306 the actual image I.sub.n
acquired in step 305 is registered with the previous image
I.sub.n-1 for generating a registration transformation
T.sub.n-1.fwdarw.n. The registered images are subtracted from each
other to create an n-th subtraction image I.sub.n,s, in step 307.
In step 308 new brachytherapy seeds are detected in the subtraction
image I.sub.n,s. In step 309 the registration transformation
T.sub.n-1.fwdarw.n is used to update prior seed locations for the
actual ultrasound image I.sub.n, wherein in step 310 the new and
prior brachytherapy seeds, i.e. the new and prior brachytherapy
seed positions, are combined in the coordinate system of the actual
ultrasound image I.sub.n. In step 311 the registration
transformation T.sub.n-1.fwdarw.n is used to update the
segmentations, and in step 312 the delivered radiation dose, i.e.
the radiation dose delivered by the new brachytherapy seeds and the
prior brachytherapy seeds, is calculated. In step 313 the treatment
plan for placing the remaining brachytherapy seeds is updated. In
step 314 it is determined whether further brachytherapy seeds need
to be deposited. If this is the case, the method continues with
step 304. Otherwise the method ends with step 315.
[0062] Steps 401 to 408 of the second embodiment of the
brachytherapy method illustrated in FIG. 9 are similar to steps 301
to 308 described above with reference to FIG. 8. Moreover, in step
409 the actual ultrasound image I.sub.n is registered with the base
ultrasound image I.sub.0 for finding a registration transformation
T.sub.0.fwdarw.n. In step 410 the transformation T.sub.0.fwdarw.n
is used to bring the previous seed positions from a coordinate
system defined by I.sub.0 to a coordinate system defined by
I.sub.n. In step 411 the registration transformation
T.sub.0.fwdarw.n is used to update the segmentations and in step
412 an inverse region transformation T.sub.n.fwdarw.0 is calculated
and used to transform the new seed positions to the coordinate
system of I.sub.0. The remaining steps 413 to 416 correspond to
steps 312 to 315 described above with reference to FIG. 8.
[0063] Some steps of the brachytherapy method described above with
reference to FIGS. 8 and 9 can be regarded as being steps of an
assisting method for assisting in performing a brachytherapy. For
instance, the electromagnetic tracking of the position of the
introduction element in steps 304 and 404 and steps 305 to 315 and
405 to 416, respectively, can be regarded as being steps of the
assisting method. Correspondingly, the electromagnetic tracking
unit 6, the ultrasound unit 7, 15, the seed position determining
unit 8, the region of interest determining unit 9, the treatment
plan providing unit 10, which may just be a storing unit, which
stores an already determined initial treatment plan and initial
segmentations and which provides the stored treatment plan and the
segmentations, and the treatment plan updating unit 11 may be
regarded as forming an assisting apparatus 1 for assisting in
performing a brachytherapy.
[0064] By updating the segmentations also a swelling of the object,
in which the introduction element is inserted, in particular, of a
prostate, can be considered, while inserting the remaining
brachytherapy seeds. In particular, the volume of the prostate
generally increases during the treatment procedure as a result of
the trauma caused by inserting the introduction element. The
deformable registration of images acquired over time enables the
brachytherapy system to measure prostate swelling and adapt the
treatment plan to compensate for the larger volume of the prostate.
The deformable registration can therefore also be used to detect
and measure edema.
[0065] LDR brachytherapy can be used to treat prostate cancer in
early stages and entails a permanent placement of radioactive
brachytherapy seeds inside the prostate to kill the cancer cells
via radiation. The positions of these brachytherapy seeds are
accurately planned preoperatively to ensure a sufficient coverage
of the target gland while sparing organs at risk such as the
urethra and the rectum. An accurate placement of the brachytherapy
seeds leads to a better treatment outcome and less toxicity.
However, in known brachytherapy systems deviations from the plan
are generally present due to problems such as prostate motion and
deformation caused by needle or catheter insertion, prostate edema,
needle or catheter bending, et cetera. Prostate swelling caused by
the trauma of needle or catheter insertion is a major source of
error as the enlargement of the prostate is not taken into account
in the initial treatment plan.
[0066] The brachytherapy system described above with reference to,
for instance, FIG. 1 provides therefore preferentially a dynamic
dosimetry and planning technique, which entails an accurate and
real-time localization of already implanted brachytherapy seeds and
a modification of planned positions and of the number of remaining
brachytherapy seeds, in order to cover up under radiated regions
and avoid over radiating organs at risk. The brachytherapy system
is particularly adapted to circumvent following obstacles in seed
detection by using ultrasound: a) the creation of a shadow in the
ultrasound image by highly echogenic seeds that can obstruct other
seeds located in the shadow area, b) dispersing an incoming
ultrasound wave by a seed away from the ultrasound probe such that
the seed appears less bright and is sparely distinguishable from
background speckle and c) seed-like image artifacts caused by, for
instance, microcalcifications in the prostate. For circumventing
these obstacles the brachytherapy system is preferentially adapted
to perform incremental imaging, which is combined with beam
steering and elastic deformable registration. Since the
brachytherapy seeds are implanted sequentially, real-time dosimetry
and planning can allow the physician to modify the positions and
number of remaining brachytherapy seeds, intra-operatively, to
compensate for possible errors.
[0067] Incremental imaging is preferentially used to identify the
positions of newly implanted brachytherapy seeds, as the
brachytherapy seeds are implanted sequentially. The brachytherapy
system may be adapted to take a three-dimensional image of, for
instance, the prostate before and after each brachytherapy seed
deposition or before and after the deposition of all brachytherapy
seeds within one needle or catheter. A group of brachytherapy seeds
may be defined by a single brachytherapy seed only or by several
brachytherapy seeds, wherein the several brachytherapy seeds may be
brachytherapy seeds within one needle or catheter. The
three-dimensional image taken before and after the respective
brachytherapy seed deposition may be produced by spatially
compounding several two-dimensional or three-dimensional images
acquired at different beam angles.
[0068] The electromagnetic tracking of the introduction element, in
particular, of the tip of the introduction element, at the time of
depositing the respective brachytherapy seed, leads to an estimated
position of the brachytherapy seed. This estimated position can be
used to narrow down the search area, when identifying the
brachytherapy seed in the subtraction image as described above with
reference to, for instance, FIG. 7.
[0069] Although in above described embodiments the brachytherapy is
mainly applied to the prostate, the brachytherapy can also be
applied to other parts, in particular, to other organs, of a human
being or an animal.
[0070] Although in above described embodiments the tracking is
performed by using electromagnetic tracking The tracking unit can
also be adapted to use another tracking technique for tracking the
position of the introduction element like fiber optical shape
sensing tracking.
[0071] Other variations to the disclosed embodiments can be
understood and effected by those skilled in the art in practicing
the claimed invention, from a study of the drawings, the
disclosure, and the appended claims.
[0072] In the claims, the word "comprising" does not exclude other
elements or steps, and the indefinite article "a" or "an" does not
exclude a plurality.
[0073] A single unit or device may fulfill the functions of several
items recited in the claims. The mere fact that certain measures
are recited in mutually different dependent claims does not
indicate that a combination of these measures cannot be used to
advantage.
[0074] Procedures like the determination of a registration
transformation, the segmentation procedures, the updating
procedures, et cetera performed by one or several units or devices
can be performed by any other number of units or devices. For
example, steps 306 to 313 and 406 to 414 can be performed by a
single unit or by any other number of different units. The
procedures and/or the control of the assisting apparatus in
accordance with the assisting method and/or the control of the
brachytherapy system in accordance with the brachytherapy method
can be implemented as program code means of a computer program
and/or as dedicated hardware.
[0075] A computer program may be stored/distributed on a suitable
medium, such as an optical storage medium or a solid-state medium,
supplied together with or as part of other hardware, but may also
be distributed in other forms, such as via the Internet or other
wired or wireless telecommunication systems.
[0076] Any reference signs in the claims should not be construed as
limiting the scope.
[0077] The invention relates to an assisting apparatus for
assisting in performing brachytherapy. The position of an
introduction element like a catheter is tracked particularly by
using electromagnetic tracking, while a group of seeds is
introduced into a living object. This provides a rough knowledge
about the position of the seeds within the object. An ultrasound
image showing the group is generated depending on the tracked
position of the introduction element and, thus, depending on the
rough knowledge about the position of the seeds, in order to
optimize the ultrasound visualization with respect to showing the
introduced seeds. Based on this optimized ultrasound visualization
the position of a seed of the group is determined, thereby allowing
for an improved determination of seed positions and correspondingly
for an improved brachytherapy performed based on the determined
positions.
* * * * *